March 12 (Reuters) - The U.S. Food and Drug Administration on Tuesday said that the antibiotic azithromycin, sold as Zithromax or Zmax, can cause a potentially fatal irregular heart rhythm in some patients.

Earlier this year a New England Journal of Medicine study compared the risk of cardiovascular death from different antibacterial drugs and found that the drug, which is made by Pfizer Inc and is also sold by generic drugmakers, had a higher rate of death. (Reporting By Caroline Humer; Editing by Gerald E. McCormick)